Bore sighting device for firearms



Dec. 11, 1956 R. ST. C. ELLIOTT BORE SIGHTING DEVICE FOR FIRE ARMS Filed June 27, 1955 2 Sheets-Sheet 1 FIG INVENTOR.

Dec. 11, 1956 R. sT.-c. ELLIOTT 2,773,309

BORE SIGHTING DEVICE FOR FIREARMS Filed June 27, 1955 2 Sheets-Sheet 2 8 INVENTOR.

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United States Patent BORE SIGHTING DEVICE FOR FIREARMS Raymond St. C. Elliott, Seattle, Wash.

Application June 27, 1955, Serial No. 518,003

9 Claims. (Cl. 33-46) This present invention relates to the general art of accessory devices for firearms and, more particularly, to a bore sighting device for rifles, and the like. This invention contemplates the employment of a cartridge-like device which may be inserted into the chamber of a rifle and which, because of its design, will accurately center on the axis of the bore a rear aperture and a forwardly disposed pair of crossed wires.

Rifiemen, whether they are target shooters or hunters, are inclined to be experimenters, to a degree at least, in order that they may perfect a hunting or target weapon which suits their particular ideas of an appropriate arm for their favorite sport. There are available to the sportsman a tremendous number of different types of rifle sights. They may be generally classified as iron sights and telescopic sights. Because of the numerous theories devolved by the proponents of the dilferent types of sighting devices, there is a tremendous interest in individual trial of these difierent devices, and these trials or experiments lead to the necessity of accurately aligning these sights with the bore of the rifle and this, in turn, can best be solved by bore sighting.

Bore sighting as used in this present application infers that the rifle is placed on some form of rest, preferably, clamped in an adjustable vise or sighting means so as the rifleman looks through the bore of the rifle, he will see the bulls-eye of the target in the center of the bore. Trials by many people have clearly demonstrated that it requires long experience and expert handling to be able to look through the bore of a rifle at a bulls-eye target and be reasonably assured that the axis of the bore is, in effect, centered on the bull. Many devices have been provided in the past to assist in this tedious and delicate operation, however, those observed have been characterized by constructions which require a higher degree of mechanical skill than is possessed by the average rifleman. Further, these devices are generally made in two parts so that one part goes on the muzzle of the rifle and the other on the breach or chamber end and unless the adjustment is accurately made the shooter would be better off merely looking through the bore of the rifle unaided by any such devices.

In this present invention means have been provided which are compact, easily operated by anyone familiar with a rifle, and which will produce results of an order having higher accuracy than is actually required. On the matter of accuracy of bore sighting, it must be remembered that few rifles will actually discharge their bullets so that they will follow the axis of the bore of the rifle barrel. There are many factors that cause the rifle, in its firing, to throw the bullet otf the line formed by projecting the axis of the bore. Naturally, in all firing the force of gravity is constantly acting on the bullet so the bullet must be discharged actually at an angle upwardly from the shooters target line. Then there are many other forces brought into play. The vibrations set up in firing causes a whip in the barrel which may throw the bullet or start it in its line of flight considerably out of the intended direction. The bending of a stock, the holding characteristics of the shooter, the tightness of his sling, if the same is used, all contribute to a mechanical error principally even though the rifle is accurately bore sighted there will alvlvlays be a few minutes of deviation from the line of sig t.

It is therefore the prime requisite of a bore sighting device that it will assure that the bullet hit a reasonable sized target at a reasonable range. Much bore sighting is done at yard range, and if a bore sighting device will place the center of impact reasonably near the center of a thirty inch square target, it has well fulfilled its purpose and will permit the rifleman then to make the accurate final adjustments with the minimum use of ammunition, which today has reached a cost that forms quite a deterrent to rifle shooting. It is believed that this present device adequately fulfills the need of bore sighting device for rifle shooters.

A principal object of this present invention is to produce a bore sighting device which is small, easily carried, not subject to damage, and which can be used with a very minimum of technical knowledge on the part of the shooter.

A further object of this invention is to produce a bore sighting device which will adapt itself to a wide variety of chamber sizes and thus provide a device that will be capable of accurate positioning in the chamber for any one particular cartridge, even though the chambering of the diflerent manufacturers varies through a wide range of allowable tolerances.

A further object of this invention is to provide a bore sighting device which will accurately center the front portion of the device on the head spacing cone of the chamber and, further, provide that the rear of the device will be equi-distance from the walls of the chamber.

Further objects, advantages and capabilities will be apparent from the description and disclosure in the drawings, or may be comprehended or are inherent in the device.

In the drawings:

Figure 1 is a perspective view illustrating one manner in which my device may be employed;

Figure 2 is a pictorial representation in which the view as seen by the rifleman through the bore of his rifle and through his line of sighting on top of the rifle are superimposed upon each other;

Figure 3 is an elevation, in section, showing my bore sighting device in the chamber of a military type of rifie;

Figure 4 is a rear elevation of my bore sighting device;

Figure 5 is a longitudinal sectional view, in perspective, illustrating the internal construction of my device;

Figure 6 is a perspective view, illustrating the cross wire holding element of my device;

Figure 7 illustrates one of the resilient centering means employed in my device;

Figure 8 illustrates the use of my device in a military type of bolt action rifle.

Referring more particularly to the disclosure in the drawings, the numeral 10 designates the cartridge caselike body member of my device. This member may be made of any suitable material. In its cheapest form it might be made from a cartridge case of the caliber for which the device is desired to serve. Ordinarily, however, the brass cartridge cases are not of best proportions in that they are relatively heavy near the base or primer end and then feather out to a rather thin wall near the neck end of the case. course, to provide the greatest degree of obturation for the gasses generated on firing of a cartridge.

A preferred arrangement is to make body 10 of heavier wall construction to the end that it will not be easily deformed. Suitable materials are the non-ferrous brass This construction is employed, of

alloys or the preferably non-corrosive or stainless steels.

The case is provided with a neck portion 12, which should be undersized slightly for the chamber with which it is to be used. The body proper, 14, should generally conform to the shape of the cartridge case of a caliber in which the device is to be used, but preferably, it should be considerably smaller in diameter than the standard cartridge so that it may fit any of the various guns chambered for that particular cartridge. The examination of rifles show that the different manufacturers have a wide range of tolerances for their chambering. As an example, the popular military cartridge designated as the 30-06 may be chambered with a tolerance of from two to eight-thousandths of an inch. This wide range of tolerance is desirable in many instances because, after all, it is essential that a gun perform with certainty and this reliability of firing requires that the chamber be big enough to accept any standard cartridge made by any of the recognized manufacturers. The chamber, normally is made larger on hunting rifles than on target rifles, because in hunting, particularly, the cartridge cases may pick up a certain amount of grime or corrosion which would make them fit too tight in a standard minimum chamber. On the other hand, a target shooter may handload his own ammunition and by exercising care in the maintenance of his ammunition, he can have his rifle chambered to a tolerance of two or three thousandths in the diameter. It is because of this range of chambering tolerances that an ordinary shell case put into the chamber of a rifle will not have its axis in coincidence with the axis of the bore as projected into the chamber. For this reason it is desirable that sufficient clearance be provided as at 16, in Figure 3, so that centering means may be provided in body 14, to insure the coincidence of the axis of the bore sighting device and the axis of the chamber.

A very satisfactory arrangement of centering means is illustrated in Figures 3, 5, and 7, and consist of, preferably, three wire fingers, as 20, which are fixedly anchored at one end in the body 14, as at 22. A preferred construction is to employ drilled holes in body 14, and to employ an elongated washer element, as 24, which can be fixedly secured to the upturned end 26 of member 20, and this will give adequate rigidity so that when the device is brazed or soldered in place, as indicated at 28, a firm anchorage will be provided. Body 14 is slotted longitudinally, as at 30, to provide an opening through which the V portion 32 of member 20 can project and thus engage the inner surface of chamber 34. Fingers 20 are preferably made of a well tempered spring wire and it is essential that the protrusion of the V portions 32 be uniform and of equal amount for each of the three devices used in order to insure concentricity of the device in the chamber.

Body portion 14 and neck portion 12 are joined by a conical portion 36 normally termed the cartridge shoulder. The angle of this cone should conform very strictly to the cone of the cartridge used in the rifle under consideration. On a 30-06 cartridge this included angle is 34 degrees and 26 minutes. it is desired to make it clear that this is one point where accuracy is essential as the accuracy of the device is, to a degree, dependent upon the cone of the device seating fully in the cone of the chamber, much as a head space gauge would seat.

At its rear end, body 14 should conform, in general, to the exterior dimensions of a cartridge case, excepting that it is relieved in part so that the centering fingers 20 can properly function but it is desirable that the rear flange, as 40, be accurately sized to equal the cartridge used in the rifle. This is desirable in order that proper engagement may be had with the extractor of the bolt or breech mechanism of the rifle and by free-standing so any portion of its periphery may be engaged and thus provide a convenient means for removing the same.

At the front end of my device I provide the cross wires, as 42 and 44. These wires should be relatively fine so that they will not cover up too much of the target when bore sighting is being done. The exact size of the wires will vary in accordance with the range used, but most especially, in accordance with the distance the viewing eye must be from them. In the average rifle, as viewed in Figure 8, the users eye probably will be at a point about above the tip of the comb, indicated at 46, and aligned with the bore. When so viewing the target through the device, the wires themselves should not cover in excess of one-half a minute of angle on the target, as that would equal one-half inch of the target at yards. In order to insure accuracy, the interior of neck 20, as 50, should be accurately bored as distinct from reaming so that this bore will be truly concentric with the seating cone 36. Adapted to seat within bore 50 is a bushing member 52, to which cross wires 42 and 44 are accurately affixed. The wall of bushing 52 is preferably throughdrilled for the wires which are then stretched through the openings and soldered or brazed in place. Suitable jigs should be provided to insure the maximum accuracy of the positioning of the wires 42 and 44, as a small error at this point will be magnified considerably at the target. Bushing 52 is provided with a flange to insure its proper seating, as 54, to the end that the bushing may be seated, preferably, just friction tight in the end of bore 50. If it is found desirable, bushing 52 may be suitably fixedly positioned in bore 50.

The base 41 is provided with a through opening, as 45, which should be accurately positioned on the longitudinal axis of body 14. This opening corresponds to the position of the flash hole of the cartridge case but in this instance the diameter of hole 45 should be determined not by the diameter of the usual flash opening, but by the viewing distance that is imposed upon the bore sighter by the particular type of rifle action he is sighting with. In the case of a bolt action rifle, following the showing of Figure 8, the eye will be quite removed, whereas in a single shot rifle it might be possible to get the eye quite close to the opening. It follows that the further back the eye must be positioned, the larger should this opening 42 be, in order that an adequate amount of light will be passed through to make the device operable in a satisfactory manner. Experience has shown that the size of opening 45 quite often corresponds to the flash opening of the cartridge case. For the Springfield cartridge, the usual primer flash opening has a diameter of .078 inch which is normally about the minimum diameter that can be practically used in varying light conditions.

In using this device the rifle must be adequately sup ported as by a suitable box or stand 60, with adjustable means as wedges 62 so that the rifle can be accurately aimed on the target and will be supported in that position without any holding on the part of the rifleman. For use on a bolt action rifle it is desirable that the extractor be removed from the bolt and then the bore sighting device inserted, preferably, by hand into the rear of the chamber, after which the bolt is moved forward to seat the device on the forcing or head spacing cone 64. This manner is normally preferable in endeavoring to seat the device by hand in that the chamber of the average rifle is well within the breech ring of the action and difiicult to reach by hand. Of greater importance from an accuracy standpoint, however, is that the bolt face is accurately at right angles to the axis of the bore. Consequently, as the bolt face contacts the face of rim 4%] it practically insures that the bore sighting device will be accurately positioned within the bore once the cone portion 36 has been seated upon the forcing cone 64.

The shooter should then remove the bolt, leaving the bore sighting device in the chamber and take his position behind the rifle and adjusting its position, so that he sees the bulls-eye, as 66, through the bore and can place the image of the cross-wires 42 and 44, as 68, on the desired part of the target. In Figure 2 a six oclock hold is shown. With the axis of the bore thus aimed at the appropriate part of the target T, the rifleman now adjusts his sights to the same position. In Figure 2 a post front sight, as 70, is indicated as though it were being viewed from an open or aperture sight at the rear of the rifle. With the iron sights there is a wide variety of means that may, and many times must, be applied in order to shift the sights to get this composite picture, as indicated in Figure 2. Certain sights are provided with micrometer adjustments, others require such basic treatment as a file or a drift and hammer in order to achieve the alignment. Between these two extremes are many other means of adjusting the sights. In the case of a telescope sight, the adjustment is usually much easier effected and here again, the reticle of the telescope should be positioned at the same point indicated by the cross-wires 42 and 44, or more properly their image, as indicated at 68 in Figure 2.

When the rifleman has the bore of his rifle and his sighting arrangement meeting at the same point on the target, he has achieved everything that can be done by bore sighting and it will then be necessary for him to fire groups of shots so that his center of impact can be determined and then make the appropriate changes in his sighting means. Experience has shown, however, that with an accurate aid in bore sighting as provided with this present device, that bore sighting is reduced to a manner of minutes, normally, and the amount of ammunition expended to get shots near the center of the target is reduced to a very minimum. This savings in time and ammunition is greatly appreciated by the serious rifleman and indicates the true worth of a device of this order.

It is believed that it will be clearly apparent from the above description and the disclosure in the drawings that the invention comprehends a novel construction of a bore sighting device for firearms.

Having thus disclosed my invention, I claim:

1. A bore sighting device for use in the chamber of hand firearms, comprising: an elongated and hollow cartridge-shaped body having a cylindrical end or neck portion, and a conical shoulder portion adjoining said neck portion adapted to coact with the firearm shoulder cone to center the forward portion of the body in the rifle bore; said body having corresponding diameters less than the cartridge adapted for use in said chamber; resilient centering means at the rear portion of said body adapted to engage the chamber walls to center the rear portion in the chamber; said body having forward and rear center indicating mechanical sighting means in its interior aligned with the axis of said body and said body having axial openings at the front and rear thereof for sighting therethrough at a target.

2. The subject matter of claim 1 in which said body has a free-standing cartridge type rear flange whereby the body can be engaged by the extractor of the firearms.

3. The subject matter of claim 1 in which said sighting means include cross wires at the forward end thereof and a peephole at the rear end.

4. The subject matter of claim 1 in which said rear centering means comprises three radially spaced wire spring fingers secured at one end to the interior of said body and having their other ends free and acting through slots in said body to contact the chamber walls.

5. A bore sighting device for use in the chamber end of a firearm barrel, comprising: an elongated hollow cartridge shaped body smaller in diameter than the cartridge adapted to said chamber having resilient centering means at its rear portion in the rifle chamber and at its forward portion a conical portion to center the body with the forward portion of the chamber and its axis aligned with the axis of the firearm bore, and said body having forward and rear spaced center indicating mechanical sighting means in its interior aligned with the axis of said body and the ends of said body having openings permitting sighting therethrough and through the bore at the target.

6. The subject matter of claim 5 in which said centering means at its rear portion comprises a series of radially spaced wire spring fingers.

7. The subject matter of claim 6 in which said wire spring fingers have inner ends secured in radial openings in said body and extend inside of the body from said inner ends out through slots in said body and having reversely bent free ends whereby the fingers press on the chamber walls in the area of said bends.

8. The subject matter of claim 5 in which said body has a free-standing cartridge type rear flange whereby the body can be engaged by the extractor of the firearm at any part of its periphery.

9. A bore sighting device for use in the chamber of firearms, comprising: an elongated hollow body having a diameter less than said chamber, said body having a tapered forward portion adapted to coact wth the firearm chamber shoulder cone to center the forward portion of the body in the bore, resilient means for centering the rear portion of said body in said chamber, said body having forward and rear center indicating sighting means in its interior aligned with the axis of said body and said body having openings at the front and rear thereof for sighting therethrough and through the bore at the target.

References Cited in the file of this patent UNITED STATES PATENTS 793,131 Henkes June 27, 1905 953,696 Konig Apr. 5, 1910 1,035,426 Dixon Aug. 13, 1912 2,294,913 Kaufman et a1 Sept. 8, 1942 2,548,861 Brown Apr. 17, 1951 FOREIGN PATENTS 731,183 Germany Feb. 19, 1943 

